Competitive interactions were studied among three exotic predators of the hemlock woolly adelgid, Laricobius nigrinus, Pseudoscymnus tsugae and Harmonia axyridis, in laboratory and field trials in southwestern Virginia from June 2002 to September 2003. Results of laboratory trials showed that some predator combinations were more susceptible to intraguild predation than others, and that such behavior was affected by environmental conditions and prey densities. Early season field trials (March-May), involving single and multiple predator combinations, showed low levels of intraguild predation such that overall predator survival, reproduction, and feeding efficiencies were not significantly affected. On-going late season field trials (June-August), if consistent with the results of laboratory studies, would likely show higher levels of intraguild predation and significant competitive interactions. These studies will assist in optimizing release strategies for biological control agents of the hemlock woolly adelgid in the southeastern United States.
Species 1: Coleoptera Derodontidae Laricobius nigrinus
Species 2: Coleoptera Coccinellidae Pseudoscymnus tsugae
Species 3: Coleoptera Coccinellidae Harmonia axyridis (hemlock woolly adelgid)
Keywords: biological control
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